[jeherr]

> And it wasn’t optimally transmissible among humans for the better part of last year. Rather, new, more efficient variants have evolved around the world. To name one example, the highly transmissible variant of SARS-CoV-2 first reported in India (B.1.617.2, or Delta) has mutations in the nucleotides encoding its furin cleavage site that appear to make the virus better at infecting cells.

My (very limited) understanding is that when a virus jumps species it is usually pretty “unoptimized” for the new host species and spends a bit of time evolving into something more fit for survival in the new host, and that this is a bit different than a single mutation way down the line during the pandemic increasing transmissibility. Maybe to be more succinct, the pro-lab leak argument isn’t that it was perfectly optimized for transmissibility in humans, but that it was already highly optimized, which is unusual.

Wouldn’t we have likely seen signs of this virus long before we did in the case of a natural origin, before it became so efficient at transmission among humans? Isn’t this what happened with the first SARS virus?